Means for controlling the amplitude of alternating current



1 .E. R. HENTSCHEL 1,305,453-

ANS FOR CONTROLLING THE AIPLITUDB OP ALTERNATING CURRENT Filed Nomi. 1929 2 Sheets-Sheet -1 l l l Pumr, m/f' INVEN TOR.

.4 TTOR EY May 12, 1931. E. R. HENTSCHEL IIEANS FOR CONTROLLING THE AMPLITUDE OF ALTERNATING CURRENT Filed Nov. 7, 1929 2 SheetS -Sheet g m HHH INVENTOR. @WM 31 M06 BY 1 ATTORNEY.

at the receiver.

Patented May. 12, 1931 entrenactate ERNEST, n. HENTSGHEL, or wnsnmcron, DISTRICT or eotvnma; JOHN onsoni AD-i eateries-Enron on se1n nnnnsr; n nmvrsonnn, nncnrcsnn; sssienon name, we, on NEW YORK, lv y n CORPORATION 70F nnnnwenn MEANS ron conrnommo Tran "AMPLITUDLE -O F; rmr nnnnrmo cunnnnm V a lica ion-fil dnovellar 7, v1929. Serial No. comes.

invention, relates broadly to radio receiving systems and more particularly to ;a

circuit arrangement for automaticallycom trolling the amplitude ofalternating currents in a radio receiving system. i 1

One of the objects of my inventioni's to provide a radio receiving system having means for controlling the volume of therep-roduced signaling energy in accordance with the amplitude 0f the Another object of my invention is to pro vide a circuit :arrangementfor a radio're in the sound reproducingzsystem for regulat ingthe amplitudeof the energy which is im pressedupon the receiving circuitiinaccord I ance with the strength of the i ncoming"signaling energy. V I.

A further object of 'my in'ven-ti'on is to pro videa thermostatic system :controll'ed by the amplitude of the alternating current: in the sound reproducing system of a radioreceiving circuit for regulating theaamplitudeflof; the signaling {energy which maybe impressed upon the signalreceiw'ng circuit :and'thn's controlling the volume of the reproduced sound. V

Otherand further objects-of my invention reside in the method of volume control in' a radio broadcast receiver as set forth more particularly in the specification hereinafter following by reference to the accompanying drawings, in which V f Figure 1 schematically and diagrammatically illustrates the principle of my invention; Fig. 2 showsa modified arrangement of the regulating means employed for efiectingvolume control in the receiving system of my'invention; and Fig. 3 shows my inven, tion applied to a radio broadcast 'receiver for controlling the volume of reproduced system in accordance with: incoming signaling energy;

In radio broadcast receivers the tuning of the receiver from one frequency setting to another is accompanied by considerable :noise and undesired interference, asthe broadcast ing stations operating on cliiferent'channels signaling energy j p I 5 nioveme'nt of; the tuning jcontrol brings in the amplitude the are quickly tuned in'and out as the receiver is tuned through aparticul'ar band of ire quencieswW'h-e'n distant stations are to be received; the receiver-is.maintained in its most'sensitive condition and considera b'le noyances experienced/When the tuning c'on- Y trol; is' operated through frequency settings Which-Will permit response to local stations at f 'severe volume; .7 The result produced not entertaining but extremely annoying as fragments of a series :ofdii'fierent programs which is often a source ofdistraction because of'the jl'oudness of; the reproduced sound when the-receiver rs mainta ned in its sensitivecondrtion.

:ro VI-IBED T Bymyinvention.Fprovidemeansiforrauto v mati'callycontrolling the amplitude an.

I signaling, energy K in the sound reproducing system. That 'is, under conditions. of strong I signals,'ithefamount of energy supplied' to the receiving circuit from the radio frequency 'energy collecting circuit will be reduced to a predetermined :value for the op eration'roi the. sound reproducer I system at that amplitude which will insure reproduction of sound at the proper volume. In the case of relatively weak sounding production on distant stations, 7 the/circuit o f invention automatt,

:cally operates to lace the receiver in its.

most sensitive condition for the reproduction of soundyat the maximum value which is' obtainable. When the receiver is tuned from one frequency setting to another, the extreme sensitivity otthe. receiver for weak signal's'isnot detrimental in that the condition of-the receiver is automatically changed when signaling energy o'iigreater-strength is received, so that reproduction of soundifor localstations may' be at the same volume as that of extremely di staint stations. Tli-e'fvolnine control of my invention is entirely can mati'c and does not depend'u pon the skill or the operator "in adj listing cathode heating ceiver istunedf I otential 'for theiform of control as the re i Referring to the'dr'awings' in more detail;

reference character- 1 designates an antenna system whiehiinclu-des primary winding 2 off 7 high frequency transformer 3.; and ground 22 which is wound around shaft 21.

connection 4 through the variable coupling condenser 5. The transformer 3 has secondary winding 6 which connects through the signal receiving circuit. In the diagrammatic showing in Figs. 1 and 2, I have illus-- trated by broken line 7 the connections to the signal receiving circuit which ultimately terminate in a final stage of power amplification which I have designated by electron tube 8. The electron tube 8 includes cathode 9 heated by any suitable means such as battery 13, control electrode 10 and plate 11. The output circuit which extends between plate 11 and cathode 9 includes the sound reproducing device 12, the source of plate potential 14, and the primary winding 15 of of the coupling condenser 5 by means of a flexible cord 22 which may be wound around shaft 21 and securely affixed thereto. A. cord 23 is wound around the shaft 21 in an opposite direction to the direction of winding of cord 22 and is affixed to the shaft 21. The opposite end of cord 23 is connected through spring 24 with the fixed support 25. The shaft 21 is journaled in suitable bearings which subject the angular movement of the shaft to minimum friction and is suitably counterbalanced as indicated at 45. The capacity elements or plates 26 which are carried by angular movable shaft 21 are light in weight and are counterbalanced by the weight 45 to allow movement of the shaft under conditions of displacement of the c'izfld e fixed plates of the variable coupling condenser 5 have been designated diagrammatically by the single plate shown at 27 and connected to the antenna or radio frequency energy collecting circuit. The movable plates 26 and shaft 21 are connected to ground at 4.

The wire 18 is selected of such size and material that the characteristics of expansion and contraction may be utilized to control the angular displacement of shaft 21. When the amplitude of the alternating current in the sound reproducing system 12 is large, the wire 18 becomes warmand elongates. Cord 22 thereupon moves to the left and by reason of the spring tension 24 under which the angularly movable shaft 21 is maintained, the cord 22 wraps upon shaft 21, while cord 23 unwinds from shaft 21, resulting in the counter-clockwise movement of the plates 26 and the decreasing of the exposure between the set of stator plates represented at 27 and the set of rotor plates represented at 26.

In. the modified form of circuit arrangement illustrated in Fig. 2, the expansive wire element 18 is firmly anchored not only at the end 20 but also at its opposite end 28. A cord 29 is taken from the center of the heater element 18 and is wrapped around the angularly movable shaft as shown at 30 in a direction 0pposite to the direction of winding of the vertically extending cord 31 which wrapped around the shaft as designated at 32. Cord 31 is maintained under tension by means of spring 33 which is fixed at its upper end as shown at 34. Under the condition of maximum signaling as represented in Fig. 2 of the drawings, wire 18 has expanded to maximumposition andthecouplingofvariablecondenser 5 is at a minimum. That is to say, the rotor plates 26 have moved to a position where there is minimum exposure with respect to stator plates 27. The position of the rotor plates with respect to the stator plates is selected with respect to the expansion and contraction of the wire element 18 to secure a maximum change in capacity in the series circuit to the antenna to control the volume of energy in the output circuit to the sound reproducer. In the arrangement shown in Fig.

2, the spring 33 takes up the slack which exists in heater element 18 as signaling energy of large amplitude occurs in the output circuit. It will be noted that the connections to the terminals 18a and 18b of the heater element 18 are sufiiciently flexible to allow expansion or contraction of the heater element 18 and operation of the angularly movable shaft 21.

In Fig. 3, the compensating system is shown disposed directly in series with the antenna 1 and above the connection to the primary 2 of transformer 3. The expansion member 18 which connects'through cord 22 to. shaft 21 connects to the secondary winding 17 and transformer 16 whoseprimary winding 15 is disposed in series with the loud speaker 12in the output circuit of the final stage of power amplification designated at 35. The radio broadcast receiver shown in Fig. 3 includes electron tubes 36, 37, and 38 connected in a tuned radio frequency cascade amplifier system in circuit with electron tube detector 39-and the audio frequency amplifier system constituting the electron tube 40 and the power amplifier electron tube circuit which connects to electron tube 35. The power supply for the cathodes of the electron tubes is obtained from any suitable source such as A battery 41. The negative bias potential for the amplifier tubes is obtained from C battery designated at 42. and the plate potential for the several tubes is obtainable from B battery system 43.

When the wire element 18 is cooled, the antenna coupling is maintained at maximum to produce maximum volume in reproduced sound in the output system. As the amplitude of the alternating current in the output circuit tends to increase, the wire element 18 gnomes."

elongates and under spring tensionfthe condenser system v operates to reduce the con-'- pling between the antenna. circuit and the receiver and thus decreasethe am Jlitudeof.

1.0.5 diagrammatically, but it will be understood.

that this shaft is mounted in bearingshaving minlmum, friction and by properly proportioning the diameter or shape ofthe shaft at a the point where the control cord wraps around the condenser shaft by means of a cam'or other device, the angular displacement of the shaft 21 through various stages of elongation of the wire element 18 may be controlled;

through a given angular distance for the 20) proper compensation of the receivingcircuit 7 said input circuit, and means in said lnput for effecting control in volume;

W ln-le I have shown the circult of invention as. applied to a radio receiving circuit,*I'

desire that it be understood that my invention may also be applied to the control'ofaudio frequency currents used in modulating broadcast transmitters and in other speeclrfrei automatic control, is

quency circuits where deslred.

brated for properlyfadjusting the operation of the compensating system "by the desired limits. In lieu of a variable condenser, I

may employ other forms of variablefimpecl ance elements and PIQVlClE'WlDlOHSiypBS of mechanical connections between the thermoelectric element and the movable element of control upon mere modulation alone. If the V ordinary" time delay is not sufficient, any of the customary damping methods, which do not increase friction, may be applied to condenser 5. Two methods of arranging the condenser may be employed: (1) Immersion in oil, and (2) the application of magnetic damping on a movable plate member, which may be either one of those used as part of the 7 variable capacity, or an additional plate secured to the rotor, adjacent one end of the shaft.

The control system of my invention will also operate in the radio frequency circuit of a receiver if sufficient amplification is employed. Winding 17 may couple to one of the radio frequency transformers, or a special.

The position off'the iotatableshaft with respect to the expansible and contractiblee'le-- mentmay be predetermined'and suitably Cali-' radio frequency transformer may be placed n one: of" the circuits. For example, such a transformer maybe placed in the plate lead of tube 38, either above or below the usual coupling transformer.

1 'While I have described preferred embodiments ofmy invention, I desire that it be -.understood that modificationsmay be made andthat'no limitations upon my invention are intended other than are imposed by the.

scope of the appended claims.

What I claim as new and desire to secure byLetters Patent of the United States is as follows:

1. In a system for automatically controlling the amplitude of alternating current, an

output circuit, an input circuit, temperature actuatedi'esponsive means insaid ouput circuit controlled by amplitude changes ln current dehvered'to said output circult from:

circuitfor controlling the amplitudeof current delivered to said input circuit, said last mentioned means beingcontrollable in accordance with the operation of said first mentioned means. V

f 2, In a system for automatically controllingv the amplitude of alternating current, anoutputcircuit, an input circuit, a circuit for; impressing variable alternating current uponsaid input circuit,thermo-electric means responsive to changes in amplitude of current in said output circuit according to corresponding changes of the current existent in said input circuit, and means connected to said-input circuit for regulating the current supplied thereto, said last mentioned means being directly controllableby saidthermo- "electric means for regulating theamplitude ofcurrent in :said output circuit.. V

system for automatically controlling the amplitude .ofalternating current,an

input circuit, an output circuit, means for supplying high frequency energy to said input circuit for controlling the operation of said outputcircuit, means connected with said input circuit for-regulating the amplitude of high frequency current suppliedthereto, and

thermo eIectricmeansv connected with said output circuit. and responsive to changes in plitudeof the effective currentin said output circuit which-is deliveredfrom said input circuit- I 4:. ,A volume controlsystemfor electron tube amplifiers in combination with a cascade amplifier circuit, having an input system andanl'output system, asound' reproducer connected to said output system,.a thermo-electrio device connectedwith said output sys tem, a signal receiving circuit connectedwith said input system,and means in said signal receiving a circuit directly controlled by said thermo-electric device in said output circuit for re ulatin the amplitude of current su u b l u b L o I plied to said sound reproducer in said output system.

5. A volume control for an electron tube amplifier having an input system and an output system, a sound reproducer connected with said output system, a signal receiving circuit connected with said input system, means in said signal. receiving circuit for regulating the amplitude of current delivered to said input system from said signal receiving circuit, and a temperature actuated member controlled by the amplitude of current in said output system for correspondingly adjusting said means in said signal reeeivmg clrcuit forregulatmg the amplitude of current whlch passes through said sound reproducer in proportion to the amplitude of signaling energy in said signal receiving circuit.

6. A volume control circuit for signal receiving systems comprising in combination with an electron tube amplifier, an input system, an output system, a sound reproducer connected in said output system, a thermoelectric device energized from said output system, a signal receiving circuit connected to said input system, means in said signal receiving circuit for adjusting the amplitude of current delivered to said input system, and means interconnecting said thermo-electric means and said means in said signal receiving circuit for automatically adjusting the amplitude of current through said sound repro-;

ducer according to the amplitude of energy existent in said signal receiving circuit.

7. In a volume control system for an electron tube amplifier, asignal receiving circuit, an input circuit connected thereto, an amplification system, an output circuit con nected to said amplification system, a sound reproducer connected with said output cir-' cuit, a thermoelectric element connected to said output circuit, means in said signal receiving circuit for regulating the amplitude of received current supplied to said input varying the coupling between said signal receiving circuit and said input circuit, said last mentioned means being controllable in proportion to the expansion or contraction of the means in said output circuit for regulating the amplitude of current supplied to said input circuit for operating said sound reproducer in said output circuit.

9. A volume control for amplifier systems, including an input circuit, an output circuit, a sound reproducer connected with said output circuit, means connected in said output circuit and expansible or contractible according to the amplitude of current in. said output circuit, a signalreceiving circuit connected with said input circuit, a variable im-' pedance for modifying the coupling between said signal receiving circuit and said input circuit, and a mechanical connection between said expansible or contractible means with said variable impedance for modifying the effect of the received signal current upon said input circuit and correspondingly controlling the operation of said sound reprt'nlucer and uniform amplitude independent of ant plitude changes in the signaling current.

10. A volume control for amplifier systems including an input circuit, an output 

